1. Field of the Invention
The present invention relates to a voltage regulator including a voltage divider circuit capable of reducing an influence of a leakage current flowing at high temperature to keep the accuracy of an output voltage of the voltage regulator.
2. Description of the Related Art
A related-art voltage regulator is now described. FIG. 9 is a circuit diagram illustrating the related-art voltage regulator.
A differential amplifier circuit 104 compares a reference voltage VREF output from a reference voltage circuit 103 and a feedback voltage VFB output from a voltage divider circuit 106, and controls a gate voltage of an output transistor 105 so that the reference voltage VREF and the feedback voltage VFB have the same value. When an output voltage of an output terminal 102 is represented by VOUT, the output voltage VOUT is obtained by the following expression.VOUT=(RS+RF)/RS×VREF  (1)where RF represents the resistance value of a resistor 121 and RS represents the resistance value of a resistor 122.
The reference voltage circuit 103 includes an Nch depletion transistor 131 and an NMOS transistor 132, and is controlled to keep the accuracy of the output voltage VOUT with respect to temperature (for example, see Japanese Patent Application Laid-open No. Hei 9-326469).
When the voltage regulator enters such a high temperature state that the NMOS transistor 132 and the Nch depletion transistor 131 that form the reference voltage circuit 103 cause a junction leakage current and a channel leakage current to flow, the reference voltage VREF is decreased due to the influence of the leakage currents (see FIG. 8A). Thus, the related-art voltage regulator has a problem in that the accuracy of the output voltage VOUT cannot be kept within a certain range at high temperature.